Introduction

An exchange address list is a collection of addressees that can be browsed by multiple types of exchange recipients to retrieve one another. An address list in Exchange 2007 is either a Global Address List, a custom Address List, or an Offline Address Book. In the first part of this article series I spoke about Global Address Lists. In this second part of this article series I covered custom Address Lists and how you can create and manage them. In the last parts of this article series I will talk about Offline Address Books in more detail.

Offline Address Books

An offline address book is a collection of address lists Exchange creates, and publishes for applications like Microsoft Office Outlook to download and use. I will first talk about the server-side aspects of the Offline Address Book, and then I will dig into the client-side of the Offline Address Book in the part of this article series.

Offline Address Book - Server-Side

OAB Properties

Every Exchange 2007 organization you deploy will have one Offline Address Book by default, the Default Offline Address Book, which includes the default Global Address List, and is scheduled to be generated every night at 5:00 A.M. Depending on the way you configured your Exchange organization (to support clients older than Microsoft Office Outlook 2003 Sp2), or if you transitioned successfully from a previous version of Exchange, the Offline Address Book will be published using Public Folders and/or the so-called Web-based distribution method.

Offline address books can be managed using the Exchange Management Console (EMC) and using the Exchange Management Shell (EMS). Using the EMC, you can retrieve the Offline Address Books in Organization Configuration underneath Mailbox, as can be seen in Figure 1.

Figure 1: Offline Address Books in EMC

General Properties OAB

Going through the properties of the Default Offline Address Book, as you can see in Figure 2, it is generated every day at 5:00 A.M. on an Exchange 2007 mailbox server called EX2007EE, and that it is the default Offline Address Book offered, meaning this OAB will be the one linked to any new mailbox database created in this Exchange organization. If you decide to create a new OAB, and set it as the default OAB, you will need to update any existing mailbox database to have the same new default OAB.

To change the schedule when the OAB is generated, you can click on the button Customize, and specify a different schedule. Outlook will update its OAB every 24 hours if not restarted. You can always update the OAB yourself using Outlook (Using Tools, Send/Receive, and then click Download Address Book), or restarting Outlook will also enforce Outlook to check if a new OAB is available for download.

Figure 2: Properties Offline Address Book - General

In order to change the server responsible for generating the OAB, you will need to click Cancel, and right-click the OAB, and select Move, as seen in Figure 3.

Figure 3: Change Generation Server OAB

You will be able to specify which Exchange 2007 Mailbox server you want to move the OAB generation process for that OAB to (Figure 4).

Figure 4: Specify the Target Mailbox Server to Generate the OAB

If you need to update the OAB, you can right-click the OAB, and select Update (Figure 5).

Figure 5: Update OAB

You will be shown a warning as in Figure 6 that updating the OAB can take several minutes.

Figure 6: Update OAB Warning

The size of the OAB can vary between a few kilobytes (KB) to more than 700 MB (uncompressed), which depends on any of the following factors according to the following Microsoft Knowledge Base article (Q841273):

Size of Active Directory: number of users and distribution groups

The information Active Directory is populated with for its users and distribution groups

The usage of certificates in a company. PKI certificates range from 1KB to 3KB, if they are present they are the largest contributor to the OAB size.

The information that is contained in an OAB, is a subset of properties of a user and a distribution group, that Outlook requires. Some of the information that is available in the Global Address List, is not included in an OAB, like any custom property you might have added in Active Directory, or group membership information. You cannot add custom properties directly to an OAB.

Address Lists

When you click on the tab Address Lists, Figure 7, you can define which Address Lists that should be included in the OAB.

Figure 7: Address Lists to include

Client Support

And when clicking on the tab Distribution (Figure 8) you can configure which OAB versions you want to have, and how you want to make them available for download. Exchange 2007 provides you with three versions of OAB you can generate, namely version 2, 3, and/or version 4.

Microsoft Office Outlook 97 up until version 2003 requires version 2, which uses ANSI characters. Version 3 was introduced by Exchange Server 2003, and added support for Unicode format. Version 3 can be used by Microsoft Office Outlook 2003 and later. Version 4 was specifically designed to remove some download issues with the OAB, and is available for any version of Outlook starting with Outlook 2003 Service Pack2.

Figure 8: OAB Distribution

Distribution Points

In Exchange 2007 you can choose the way you want your clients to download the OAB. But only Microsoft Office Outlook 2007 (and later) is able to download the OAB by connecting to a Client Access Server in your organization. If you have clients older than Microsoft Office Outlook 2007, you will need to enable public folder distribution if you want those clients to be able to download the OAB.

Web-based distribution

Once the OAB is generated by a service called OABGen, which runs on an Exchange 2007 Mailbox server, the Exchange File Distribution service, running on an Exchange 2007 Client Access server will copy the newly generated OAB files. After starting the Exchange File Distribution service, the Client Access server will poll the OAB Generation Server by default every 8 hours to see if there are new files. When Microsoft Office Outlook 2007 connects to its mailbox, it will use the Autodiscover web service to retrieve the URLs to use to retrieve Free and Busy information, configure Out of Office settings, change UM settings, and Autodiscover will also return the URL to a Client Access server to connect to for downloading the OAB using BITS.

Public folder distribution

With public folder distribution, the OAB generation process places the files directly in one of the public folders, and then Exchange store replication copies the data to other public folder distribution points. To prevent the overload when a lot of users try to download the OAB at the same time with public folder distribution, Microsoft has published a registry addition you can do to activate throttling:

There is no need to restart any service, Exchange will notice the registry key, and keep it in mind when users start downloading the OAB. But, remember, registry changes can cause serious problems and should be done carefully!

Creating a new OAB

To create a new OAB, you can use both the EMC and the EMS. Using the Shell you can add settings, you cannot specify when creating an OAB using the EMC. Table 1 lists the settings you can add, and if you can define them as well using the EMC.

Parameter

Required

Description

Available using EMC

Name

Yes

Name for the OAB

Yes

Server

Yes

Generation Server for the OAB

Yes

AddressList

Yes

Address lists to be included in this OAB

Yes

DiffRetentionPeriod

No

Allows you to define the length of time (in days) that the OAB difference files are kept on the OAB generation server and the Client Access server(s)

No

IsDefault

No

Enables you to set this OAB as the default OAB

Yes

PublicFolderDatabase

No

Enables you to define which public folder database you want to home the OAB in

No

PublicFolderDistributionEnabled

No

To enable Public Folder distribution

Yes

SkipPublicFolderInitialization

No

If using Public Folder distribution you can use this parameter to prevent Exchange from creating the required OAB system public folder when creating the OAB. During the next online maintenance cycle, the folder will be created, or when a new OAB is created, enabled for public folder distribution

No

Schedule

No

Schedule to generate OAB

Yes

TemplateInstance

No

Define a template OAB to copy when creating a new OAB

No

Versions

No

Version 2, version 3, and version 4

Yes

VirtualDirectories

No

To define the virtual directory if you want web-distribution to be enabled

Yes

Table 1: New-OfflineAddressBook Parameters

The following example shown in Figure 9 will create a new Offline Address Book called OAB-Employees, which will include a Custom Address List called Employees and is available for download using Public Folders and via the Web. The OAB will be generated on an Exchange 2007 Mailbox server called EX2007EE, and is scheduled to be updated every Monday and Wednesday between 6 A.M. and 7 A.M. Differential files will never be purged.

Figure 9: New-OfflineAddressBook

Recipients are not shown in an OAB until the OAB has been updated! You can run the EMS cmdlet Update-OfflineAddressBook to update an OAB, as shown in Figure 10.

Figure 10: Update-OfflineAddressBook

To remove an Offline Address Book, you can use the EMS cmdlet Remove-OfflineAddressBook, or the EMC, as can be seen in Figure 11.

Figure 11: Remove Offline Address Book

When removing an OAB, keep in mind that:

if the OAB has been set as the OAB for any Mailbox Database in your Exchange organization, you will need to set a new OAB for those Mailbox Databases

if the OAB has been configured as the default OAB, you will need to configure another OAB the default, or there won't be a default OAB in your Exchange organization

if an OAB is removed, you will need to manually remove any files left on your Mailbox server, and Client Access server

if you remove the last OAB, there would not be any OAB left for your users to download

Conclusion

An exchange address list is a collection of addressees that can be browsed by multiple types of exchange recipients to retrieve one another. An address list in Exchange 2007 is either a GAL, a custom Address List, or an Offline Address Book. In the first part of this article series I spoke about GALs, how you can create additional GALs, and what you need to consider to make sure your users get the intended GAL. In this second part of this article series spoke again about custom Address Lists and how you can create and manage them. In the third part of this article series I've covered Offline Address Books in more detail, to finish off the series, I will come back to the client-side of Offline Address Books.

If you would like to read the other parts in this article series please go to:

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